This invention relates to air brake systems for vehicles and more particularly to systems of this kind employing duplicated components to maintain braking capacity in the event of a line rupture or other severe leakage at some point in the system.
In furtherance of operational safety it has been a common practice to design air brake systems with at least some degree of redundancy or duplication of components so that in event of failure of one part of the system, from line rupture, severe leakage, jamming of mechanical parts or the like, at least some braking capacity may still be available through other portions of the system. More than one brake is usually provided together with more than one operator-actuated control valve or the like and means may be present to seal off portions of one side of the system from the other in the event of malfunction of the one side.
Copending application Ser. No. 695,875, filed June 14, 1976, by Henry E. Beck et al. and assigned to the assignee of this application, discloses one air brake system of this general kind in which the advantages of duplicated components are carried completely back through dual air reservoirs to the outlet of the compressor itself.
In most systems of the kind discussed above, one or more check valves provide for retaining a charge of compressed air in one or more reservoirs in the event of line rupture or severe leakage between the compressor and the reservoirs. This provides for a temporary retention of braking capacity sufficient for at least one and usually several braking cycles following the malfunction. However, following a line rupture of this kind, the compressor may no longer be able to recharge the reservoir or reservoirs as the pressurized air flow delivered by the compressor may then be partially or wholly lost through the rupture or leakage point. As a result, the pressure in the reservoir or reservoirs will eventually drop to the point that repeated braking operations cannot be continued. Warning systems are provided to alert the operator to the dropping of pressure in the reservoir or reservoirs so that corrective action may be taken while sufficient pressure remains in the reservoir to accomplish one or more braking operations. In most of these prior systems, still further fail safety is provided for in that if the operator does not take timely corrective action, the emergency brake will eventually go on automatically, as it is spring-biased to engage position and is only held disengaged by air pressure from the reservoirs.
It would be preferable if a line rupture between the compressor and one of the reservoirs did not interfere with continued charging of at least one other reservoir so that braking capacity would be retained indefinitely. This is particularly true where long flow passages are present between the compressor and the reservoirs as the possibility of rupture or serious leakage may be greater under those circumstances.